07.03.han.comment.nature

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• Publié par: Cosac
• Nombre de lectures: 108
• Langue: English

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Vol 446|5 April 2007
NEWS
Proteins make light
work of nerve control
There were audible gasps and spontaneous researchers transplanted the channel, ChR2,
applause at a neuroscience meeting in Salt into mammalian neurons. For the first time,
Lake City, Utah, in February, when Ed Boyden it was possible to stimulate a nerve remotely at
described a protein that switches off nerve speeds close to normal neuronal transmission
firing when activated by light. And when Karl (E. S. Boyden Nature Neurosci. 8, 1263–1268;
Deisseroth told the fuller story of the protein, 2005). Numerous research groups have already
called NpHR and published in this week’s begun to use this ‘on switch’.
Nature, at Cold Spring Harbor in New York The newly reported NpHR protein (see page
late last month, there was talk of a revolution 633) is exciting researchers even more. Identi-
in neuroscience. It is perhaps no surprise that fied in an archaeal species called Natronomonas
intellectual-property disputes are looming. pharaonis, it pumps chloride ions into cells,
The revolution could consign electrodes silencing physiological activity, when activated
— neuroscience’s staple tools — to the trash by yellow light. “The ‘on switch’ means we can
after a century of faithful service. They would replace the crude electrode, which stimulates
be replaced by genetically engineered proteins all types of neurons in its vicinity,” says Deisse-
that allow investigators to stimulate or inhibit roth. “But with the ‘off switch’ we can start to
very precise groups of nerves at the flick of a understand what is going on physiologically
light switch. No previous technology has come — or pathologically.” By turning off sets of neu-
close to this level of control and precision. rons in turn, researchers can investigate which
“It is incredibly exciting — now we can ones are necessary, or sufficient, to elicit a par-
really start to investigate how different neuro- ticular behaviour or response.
nal cell types contribute to the neural circuits Deisseroth and his colleagues have trans-
that mediate all sorts of behaviours,” says Carl ferred the genes for NpHR and ChR2 into the
Petersen of the EPFL Brain Mind Institute in nematode Caenorhabditis elegans, and can start
Lausanne, Switzerland. Petersen has already the worms’ swimming movements with flashes
received the NpHR protein from Deisseroth’s of blue light and stop them with yellow light.
lab at Stanford University in California and is They also showed that functional proteins are
rushing to use it in his research on sensory per- produced when the genes are injected into the
ception. “It is the best thing that has happened brains of young mice.
in neuroscience in a good long time.” In addition to his research, Deisseroth
This feeling of urgency pervades the field. holds a weekly psychiatric clinic, in which he
The technology is so powerful that leaps are assesses whether severely depressed patients
predicted in many areas. With such prizes are suitable for a treatment called deep-brain Light-activated proteins could provide a fresh
to be won, there is also a rush to publish. stimulation. In this procedure, electrodes are perspective on how nerve cells work.
Boyden, a former postdoc of Deisseroth’s who implanted deep in the brain to try to activate
left Stanford shortly after the the neuronal circuits that lift by rods and cones, to see whether this could
“It is the best thing NpHR work began and is now mood. But the technique is help restore vision.
at the Massachusetts Insti- crude and experimental, and But the immediate use for the technology that has happened
tute of Technology (MIT) in Deisseroth says that the plight will be dissecting the role of different types in neuroscience in a
Cambridge, hurried through a of his patients made him want of neurons in the circuits of both healthy and
good long time.”report last month on the activ- to find something better. diseased brains. Deisseroth plans to use mice
ity of NpHR in cultured brain The light-operated proteins that express both proteins to identify targets
cells (X. Han and E. S. Boyden PLoS One 2, might eventually replace electrodes in deep- relevant to depression, whereas Boyden plans
e299; 2007). Boyden says he thinks the idea brain stimulation, allowing physicians to hit work on mouse models of epilepsy, depression
belongs to him, but both MIT and Stanford just those neurons relevant to the disease being and Parkinson’s disease.
are pursuing patents. treated, although this would require a safe way Both researchers are distributing the NpHR
The Nature paper has resulted from a collab- to transfer the proteins into human brain cells. protein to colleagues around the world, such as
oration between researchers in Germany and The technique could also have shorter-term Sergey Kasparov at the University of Bristol, UK,
at Stanford University. It extends the collabo- clinical implications. For example, Gary Mat- who studies neurotransmitter release. When
ration’s 2005 work, conducted with Boyden, thews of the State University of New York at Kasparov heard about Deisseroth’s work, he jet-
on a channel for positively charged ions (such Stony Brook hopes to use the switches to per- tisoned a complicated plan to silence neurons
as calcium) that is found in green algae and suade retinal neurons, which don’t respond that use noradrenaline as a transmitter: “The
is activated by blue light. In that work, the directly to light, to mimic the responses elicited question we were posing is better answered by
588

NATURE|Vol 446|5 April 2007 NEWS
RACE FOR A GREEN CAR
Multimillion-dollar
X Prize set for
automotive innovation.
www.nature.com/news
Car emissions are EPA’s problem
In a major victory for states’ territory and that the months [left], they are a lame
environmentalists, the US EPA was breaking the law by duck; they are not interested in
Supreme Court this week ruled refusing to consider greenhouse climate-change regulation.”
that the federal government gases as ‘pollutants’, which it It is more likely that the
must regulate carbon dioxide has to regulate under the Clean next US president will begin
emitted from cars and trucks. Air Act. to regulate greenhouse-gas
In a strongly worded opinion The EPA denied this on a emissions through the Clean
issued on 2 April, the justices number of grounds, including Air Act, he says, if Congress
brushed aside insistence from appealing to the intentions of doesn’t get there first by passing
the Environmental Protection Congress when creating the act, climate-change laws. Certainly,
Agency (EPA) that it did not and the desirability of using the many of the Democrats in
have the authority under the promise of reducing emissions Congress would love to regulate
Clean Air Act to regulate as a lever to force developing emissions in a similar manner to
greenhouse-gas emissions countries to do the same the European Union’s Emission
from vehicles. They also — something that wouldn’t be Trading Scheme.
disagreed with the agency’s possible if the EPA was already Senator Barbara Boxer
contention that even if it had regulating them (see Nature (Democrat, California), head
the authority, it doesn’t have to 443, 486–487; 2006). of the Senate Committee on
regulate if it doesn’t want to. Lead author of the petition for Environment and Public Works,
“The use of the word Massachusetts, Lisa Heinzerling plans to call EPA officials to
‘judgment’ is not a roving of Georgetown University Law Capitol Hill later this month to
license to ignore the statutory Center in Washington DC, ask them how they will begin
text,” wrote Justice John is naturally pleased with the regulating climate change. In
Stevens. “Under the clear terms outcome: “On every single issue a statement, she said: “We
of the Clean Air Act, EPA can we won, and I think we won big.” now have a two-track process
avoid taking further action only The ruling means that the EPA for addressing global warming
if it determines that greenhouse must now evaluate greenhouse — comprehensive legislation
gases do not contribute to gases and determine whether and administrative action.”
climate change or if it provides they are “air pollution which The EPA is “reviewing the
some reasonable explanation may reasonably be anticipated court’s decision to determine
as to why it cannot or will to endanger public health or the appropriate course of
not exercise its discretion to welfare”. If it finds that they are, action”, says spokeswoman
determine whether they do.” it must regulate them. But there Jennifer Wood, adding that
Led by Massachusetts, is no timeline for how quickly it “the Bush administration has
the case was brought by must do this. The EPA under the an unparalleled financial,
several states, a handful of Bush administration “will not international and domestic
the light-activated protein technology.” environmental groups and move on it at all”, says David commitment to reducing
Another researcher keen to use the pro- American Samoa. They argued Bookbinder, director of climate greenhouse-gas emissions”
tein is David Kleinfeld of the University of that climate change was, among litigation at environmental group — a slightly bizarre contention,
California, San Diego, who is tracing the other things, causing the sea the Sierra Club, who was among to say the least. ■
neuronal pathways that mediate t